Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095;
Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095.
Proc Natl Acad Sci U S A. 2018 Jan 23;115(4):804-809. doi: 10.1073/pnas.1716315115. Epub 2018 Jan 8.
The decision of where to make an eye movement is thought to be driven primarily by responses to stimuli in neurons' receptive fields (RFs) in oculomotor areas, including the frontal eye field (FEF) of prefrontal cortex. It is also thought that a saccade may be generated when the accumulation of this activity in favor of one location or another reaches a threshold. However, in the reading and scene perception fields, it is well known that the properties of the stimulus at the fovea often affect when the eyes leave that stimulus. We propose that if FEF plays a role in generating eye movements, then the identity of the stimulus at fixation should affect the FEF responses so as to reduce the probability of making a saccade when fixating an item of interest. Using a visual foraging task in which animals could make multiple eye movements within a single trial, we found that responses were strongly modulated by the identity of the stimulus at the fovea. Specifically, responses to the stimulus in the RF were suppressed when the animal maintained fixation for longer durations on a stimulus that could be associated with a reward. We suggest that this suppression, which was predicted by models of eye movement behavior, could be a mechanism by which FEF can modulate the temporal flow of saccades based on the importance of the stimulus at the fovea.
眼球运动的决策被认为主要是由眼球运动区域中神经元感受野（RF）对刺激的反应驱动的，包括前额叶皮层的额眼区（FEF）。人们还认为，当这种活动有利于一个位置或另一个位置的积累达到阈值时，可能会产生扫视。然而，在阅读和场景感知领域，人们已经很清楚，中央凹处刺激的特性往往会影响眼睛离开该刺激的时间。我们假设，如果 FEF 在产生眼球运动中起作用，那么注视时刺激的特征应该会影响 FEF 的反应，从而降低在注视感兴趣的项目时进行扫视的概率。我们使用了一个视觉搜索任务，在这个任务中，动物可以在单次试验中进行多次眼球运动，我们发现，注视时刺激的特征强烈调节了 RF 中的反应。具体来说，当动物在与奖励相关的刺激上保持更长时间的注视时，对中央凹处刺激的反应被抑制。我们认为，这种抑制作用可以作为 FEF 根据中央凹处刺激的重要性来调节扫视时间流的一种机制，这种抑制作用是由眼球运动行为模型预测的。
